The present invention relates to N-alkyl-beta-alanine derivatives and salts thereof and, more particularly, to corrosion inhibitors having a simultaneous cleaning action that comprise an n-alkyl-beta-alanine derivative or salt thereof.
In metal working, two operations alternate with one another: forming and cleaning. Forming gives rise to new surfaces, which are particularly sensitive to exposure to water and oxygen and therefore have a strong tendency to corrode.
Corrosion inhibitors must be used in order to suppress the corrosion. A subsequent cleaning step can be carried out using an aqueous surfactant solution. These solutions are generally multicomponent mixtures comprising anionic and nonionic surfactants.
From an economic standpoint, it signifies an advancement to use a cleaning-product solution which, not only cleans, but simultaneously protects the metal against corrosion. The surfactants must advantageously be xe2x80x9cmildxe2x80x9d, i.e., the surfantants must not be listed as hazardous substances and must be readily biodegradable.
In view of the above, there exists a need for providing a cleaning product solution which serves both as a cleaner and as a corrosion inhibiting agent.
The present invention relates to N-alkyl-beta-alanine derivatives which combine a degreasing action with corrosion protection. Specifically, the present invention relates to aqueous cleaning corrosion inhibitors which comprise N-alkyl-beta-alanine compounds of the general formulae (I) and/or (II) 
in which
R is an optionally branched hydrocarbon radical having from 8 to 18 carbon atoms and optionally containing multiple bonds, which radical may optionally contain one or more hydroxyl groups,
Ra, Rb, and Rc, independently of one another, may be cations of an alkali metal group, ammonium salts or the protonated radical of an amine,
Rd is hydrogen or a C1 to C18 alkyl radical, in particular a C8 to C14 alkyl radical, which may optionally be branched and/or may contain double bonds, and the quantitative ratio of the formulae (I):(II) is from 2:0 to 0:2, preferably from 1.5:0.5 to 1:1.
In one embodiment of the present invention and when Rd is a C1-18 alkyl radical, the quantitative ratio of formula (I):(II) is approximately 0:1 to approximately 1:1.
The N-alkyl-beta-alanine derivatives used in accordance with the present invention are prepared by reacting fatty amines with acrylic acid in inert solvents under reaction conditions which are known to those skilled in the art. Depending on the chosen stoichiometry of the reactants, the monoaddition products or the biaddition products are formed predominantly. The technical reaction mixtures are generally neutralized with a base or adjusted to a higher pH without further isolation of the respective pure components.
The fatty amines used in the present invention are prepared in accordance with known methods by reacting fatty acids with NH3 in the presence of catalysts to give the nitrile, followed by hydrogenation to give the primary or secondary amine.
Fatty acids used, individually or in mixtures, include fatty acids such as caprylic acid, capric acid, 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, isostearic acid, stearic acid, hydroxystearic acid (ricinoleic acid), dihydroxystearic acid, oleic acid, linoleic acid, petroselinic acid, elaidic acid, arachidic acid, behenic acid, and erucic acid, gadoleic acid, and also the technical mixtures obtained in the pressure splitting of natural fats and oils, such as oleic acid, linoleic acid, linolenic acid, and especially rapeseed oil fatty acid, soybean oil fatty acid, sunflower oil fatty acid, and tall oil fatty acid. In principle, all fatty acids having a similar chain distribution are suitable in the present invention.
The amount of unsaturated fractions in these fatty acids or fatty acid esters isxe2x80x94where necessaryxe2x80x94adjusted to a desired iodine number by means of known catalytic hydrogenation techniques or is achieved by blending fully hydrogenated with unhydrogenated fatty components.
The iodine number, as a measure of the average degree of saturation of a fatty acid, is the amount of iodine consumed by 100 g of the compound in order to saturate the double bonds.
Preference is given in the present invention to using partially hydrogenated C8/18 coconut and/or palm fatty acids, rapeseed oil fatty acids, sunflower oil fatty acids, soybean oil fatty acids, and tall oil fatty acids, having iodine numbers in the range of approximately 80 to 150, and especially technical-grade C8/18 coconut fatty acids, in which context it may optionally be advantageous to select cis/trans isomers such as C16/18 fatty acid cuts rich in elaidic acid. These are commercially customary products and are offered by a number of companies under their respective trade names.
By controlling the proportion of the compounds of the general formulae (I) and (II) that are used, it is possible to adjust the degreasing/corrosion protection properties. For example, with increased proportions of the compounds of the general formula (II) in which Rd is an optionally branched alkyl radical optionally containing double bonds, or alkenyl radical, having in particular from 8 to 14 carbon atoms, formulations are obtained which not only exhibit a sufficient degreasing capacity, but give rise to excellent corrosion protection.
Preference is given in accordance with the present invention to compounds in which Ra, Rb and Rc=(Na, K or the protonated radical of an amine, preferably of a mono-, di- or trialkanolamine), such as, for example, monoethanolamine, diethanolamine, especially triethanolamine, monoisopropanolamine, diisopropanolamine, methyldiethanolamine, methylethanolisopropanolamine, or mixtures thereof.
The ratio of Na, K, ammonium to protonated radical of an amine may fluctuate within wide ranges and is codetermined by the radical R and the proportion of the formulae (I) and (II). Specifically, the ratio of Na, K, ammonium to protonated radical of an amine is chosen in any case so that the water solubility of the compounds, as well as a sufficient cleaning power and corrosion protection, is ensured.
In order to formulate the aqueous corrosion inhibitors of the present invention, the compounds of the general formulae (I) and/or (II) are used in amounts of from about 0.1 to about 5% by weight, in particular from 0.5 to 3% by weight. It is also within the contemplation of the present invention to use any auxiliaries and additives which are well known to those skilled in this field, in the known, customarily employed concentrations. For example, auxiliaries and additives such as emulsifiers, foam regulators, biocides, and antioxidants may be employed in conjunction with the inventive aqueous cleaning corrosion inhibitors of the present invention.
The following examples are given to illustrate some advantages of the present invention.